Bones and bony structures are susceptible to a variety of weaknesses that can affect their ability to provide support and structure. Weaknesses in bony structures may have many causes, including degenerative diseases, tumors, fractures, and dislocations. Advances in medicine and engineering have provided doctors with a plurality of devices and techniques for alleviating or curing these weaknesses.
The cervical spine has presented the most challenges for doctors, partially due to the small size of the vertebrae and the spacing between adjacent vertebrae. Even throughout the spine, because of its proximity to the spinal nerve and the importance the spine plays in day-to-day activities, correcting spinal disorders requires reliable and effective treatments.
Typically, weaknesses in the spine are corrected using devices that fuse one or more vertebrae together. Several artificial materials and implants have been developed to replace the vertebral body, such as, for example, titanium cages, ceramic, ceramic/glass, plastic or PEEK, and carbon fiber spacers. Recently, various expandable prosthetics or expandable cages have been developed and used for vertebral body replacement or in conjunction with other fusion procedures.
During fusion or other corrective procedures, bone plates or other stabilization systems are used to help maintain rigidity of the treated area, maintain compression between adjacent vertebrae, and fix or stabilize the area being fused. One such example is disclosed in U.S. patent application Ser. No. 11/464,625, which is incorporated herein by reference. Thus the bone plate is attached to two vertebrae to secure the area of fusion. As plates are often constructed of a single material, they are stable, strong devices.
In other instances, staples, anchors, and rod assemblies are used to stabilize the area being fused. Under these procedures, staples are placed into the adjacent vertebra with anchors. Titanium rods may then be fixed to the staple/anchor assemblies. One such system is disclosed in U.S. Pat. No. 6,986,771, which is incorporated herein by reference. Stabilization techniques involving rods allow for customization during implantation and a greater degree of control over placement, tension, load, and other important characteristics known to those of skill in the art.
Design considerations for fixation systems include ease of use, stability, ability of the surgeon to customize during implantation, and ability of the fixation system to allow for compression. Past fixation system designs have not necessarily alleviated all of the problems. Accordingly, a need exists for fixation systems that can provide a surgeon and patient with stable, customizable fixation systems.